Documents de présentation
Driven-dissipative quantum fluids of light, experimentally realised in for example semiconductor microcavities, circuit or cavity QED systems, provide a unique testbed to explore new non-equilibrium quantum phenomena. I will review recent progress in this field. In particular, we show that polariton quantum fluid can exhibit a non-equilibrium order, where superfluidity is accompanied by...
Après relaxation, un système quantique intégrable, en particulier un gaz unidimensionnel de bosons, est caractérisé par la distribution de rapidités, une grandeur préservée au long de la dynamique. La distribution de rapidités n'est rien d'autre que la distribution asymptotique des impulsions des particules après une expansion unidimensionnelle du système. Cette définition est directement liée...
Les gaz de fermions de spin 1/2 font l'objet actuellement d'une controverse intéressante sur une question fondamentale (et non triviale compte tenu de la force des interactions) : selon les auteurs, ces gaz présentent ou ne présentent pas de branche d'excitation collective de Higgs dans leur continuum de paire brisée ; citons le travail de Laura Benfatto (PRL 115, 157002 (2015)) dans la...
Exciton-polaritons are short-lived hybrid bosonic quasiparticles generated by the coupling of the electronic excitations of a semiconductor and light in an optical cavity. A steady state can be obtained by driving the system with an external laser compensating the photon loss [1]. If tuned above some threshold power, the laser driving triggers the Bose-Einstein condensation of...
Ultracold atom experiments enable the study of quantum systems in a very controlled and tunable environment. In particular, they offer a natural playground for the study of superfluid dynamics, made possible by the existence of interactions between atoms. Superfluids are characterized by an ensemble of specific properties, including the absence of viscosity, existence of a critical velocity...
The Kardar–Parisi–Zhang (KPZ) equation[1], originally derived to describe the kinetic roughening of growing interfaces is a stochastic non-linear differential equation that applies to a large class of non-equilibrium systems, ranging from the growth of nematic liquid crystal clusters, of bacterial colonies, or the propagation of a combustion front. Interestingly the spatial and temporal...
Analog Gravity experiments aim at observing effects initially predicted by quantum field theory on curved space time such as the Hawking effect and rotational superradiance in systems at laboratory scales with similar dynamics [1]. The high tunability of such systems enable to shed light on phenomena that are either currently eluding our comprehension or simply unreachable by their very...
Optical vortices, like Laguerre-Gauss beams, have the particularity of propagating with a helical wavefront. In addition to the polarization and the wave vector, they carry a so-called Orbital Angular Momentum (OAM). This quantity is quantized and represents a challenge for quantum technologies.
In our approach, we are interested in the conversion of the OAM during a four-wave mixing...
At zero temperature, a Galilean-invariant Bose fluid is expected to be fully superfluid.
We investigate theoretically and experimentally the quenching of the superfluid
density of a dilute Bose-Einstein condensate due to the breaking of translational (and
thus Galilean) invariance by an external 1D periodic potential. Both Leggett’s bound
[1] fixed by the knowledge of the total density and...
English
Just like Van der Waals gases, quantum gases have some universal thermodynamic properties in deviation to the ideal gas. A dilute quantum fluid of neutral particles has an equation of state involving very few intrinsic parameters. The use of mixtures – classical or quantum – of two Bose-Einstein condensate allow for the diminution or even cancellation of some terms in the dynamical...
